Polar Vortex explained

With the recent blast of arctic air impacting much of the country, you are likely familiar with the term ‘polar vortex’, but do you know what it is?  We recently sat down with Dr. Stuart Foster of WKU, Director of the Kentucky Climate Center, to look at the science behind the atmospheric feature.

“I think when you hear that term ‘vortex’, that’s kind of a scary term,” says Dr. Foster. “So it’s not to be equated with a storm like a tornado or hurricane at that scale, but this is just a much larger circulation feature in the atmosphere.”

Polar vortex has gained mainstream popularity over the last few years with a few notable Arctic blasts.  You can’t see it, but as we’ve seen recently, you can surely feel the effects from it. So if it’s not a storm or something at the surface, what is it?

“There is a pool of cold air in the polar area,” explains Dr. Foster. “And typically that is contained largely by the jet stream and really tends to keep it separated from the mid-latitudes. But occasionally as that jet stream weakens in velocity and meanders, you can get an outbreak of that very cold air that comes down to visit us.”

Along with understanding what it is and how it works, it’s just as important to realize that not every cold spell is caused by a polar vortex. Dr. Foster says that the general weather pattern can bring below normal temperatures throughout the year outside of an influence from the polar circulation.

“The polar vortex tends to be a much more intense event over a large area.”

During the most recent polar vortex event, many locations across Kentucky experienced their coldest temperatures of the season. According to Dr. Foster, however, this event could have been far worse had there been excessive precipitation involved.

“Typically when we get a Winter storm with very cold, Arctic air coming in behind it, then our temperatures drop quite a bit more because of that snow cover, but we really didn’t have that this time so that really saved us to a great extent.”

Dr. Foster also says that it is not unusual for Kentucky to get below zero, which happens once every couple of years, but it is fairly rare to have temperatures significantly below zero like places across the upper Midwest.